Weed Potential 
As a weed Water Hyacinth is wide spread throughout the world and has been declared a noxious weed throughout Australia. It infests slow-moving fresh water rivers or dams on or near the coast forming a dense mat excluding light and reducing oxygen and temperature levels.  

It inhibits the development of native aquatics plants and reduces the habitat for native invertebrates, fish, birds and limits access to native animals. 

Infestations also reduce water flow and quality, blocking drains and equipment used for pumping. The plant can reproduced rapidly by seed or by stolons with up to 2 million plants per hectare with the main growth occurring throughout summer. 

The seeds may remain dormant in the mud for up to 15-years or longer and can germinate to re-infests cleared waterways.  

Control methods include physically removing small infestations and placing them on land to dry out.  

If seed heads are present they should be collected and placed at an authorised waste disposal site. Large infestations are difficult to remove as their combined weight is excessive and machinery is required. 

Chemical sprays may be used under the supervision of the local conservation or agricultural department.  

Biological control agents have been used in warmer climates with some success.  The physical removal of plant from the watercourse is superficial as seeds that are embedded in the mud can soon germinate and re-infest.  .